UNIVERSITI PUTRA MALAYSIA
SYNTHESIS AND CHARACTERISATION OF CARBON NANOMATERIAL ON SHORT CARBON FIBER BY FLUIDIZED BED
CHEMICAL VAPOUR DEPOSITION AND FABRICATION OF CARBON NANOCOMPOSITE
MAHTA SADEGH VISHKAEI
FK 2009 96
SYNTHESIS AND CHARACTERISATION OF CARBON NANOMATERIAL
ON SHORT CARBON FIBER BY FLUIDIZED BED CHEMICAL VAPOUR
DEPOSITION AND FABRICATION OF CARBON NANOCOMPOSITE
By
MAHTA SADEGH VISHKAEI
Thesis Submitted to the School of Graduate Studies, Universiti Putra Malaysia,
in Fulfilment of the Requirements for the Degree of Master of Science
OCTOBER 2009
ii
Abstract of thesis presented to the Senate of Universiti Putra Malaysia
in fulfilment of the requirement for the degree of master
SYNTHESIS AND CHARACTERISATION OF CARBON NANOMATERIAL
ON SHORT CARBON FIBER BY FLUIDIZED BED CHEMICAL VAPOUR
DEPOSITION AND FABRICATION OF CARBON NANOCOMPOSITE
By
MAHTA SADEGH VISHKAEI
October 2009
Chairman : Dr. Mohamad Amran B. Mohd Salleh
Faculty : Engineering
Although there are some researches on the whiskerization of CNPs on carbon fiber,
but none has studied it in the fluidized bed. This research has carried out to study the
whiskerization of carbon nanoparticles on short carbon fiber by fluidized bed reactor
chemical vapour deposition (FBCVD). The CNP whiskerized CF was added by
appropriate amount of Polypropylene to make a composite. Some information about
catalyst, nanostructural features of nanoparticles and composite discussed. Hence, in
this work, experimental studies were carried out to elucidate the influential
parameters and investigate the influence of (i) synthesis temperature, (ii) catalyst type
(iii) carbon source gas flow rate on CNP quality in FBCVD process. The synthesis of
carbon nanoparticles (CNPs) have been done by the catalytic decomposition of
acetylene over Fe/CF catalysts in a fluidized bed reactor. The general growing
conditions were: 40 L/min flow rate, 450-650°C synthesis temperature, atmospheric
pressure and three gas compositions: 50% , 25% and 25% C2H2/H2/N2. The catalyst
substrate was carbon fiber with different sizes (1mm and 2mm) and metal catalyst
with different content of iron (0.23%, 1.8% and 4.92%) were used to deposit on the
CF surface. Characterization of the catalysts and the products was performed by X-
iii
ray diffraction patterns (XRD), scanning electron microscope (SEM) and thermal
gravimetric analysis (TGA). An apparent relationship was found to exist between the
metallic iron content of the catalysts, substrate size, and the final characteristics of the
carbon products. Then the composite was prepared with the best percentage of
whiskerized carbon fiber and polypropylene with concentration of 2% and 98%
respectively. The mixture introduced into the mixer (The rotor speed and temperature
were set at 120 rpm and 180oC, and mixing continued for 10 min). Finally the
composite was analyzed by Dynamic Mechanical Analysis (DMA) for mechanical
properties. This study indicates that the optimum condition for the growth of CNP on
CF is 600 °C for 1.8% Fe on carbon fiber with 2mm length for a 30 minutes
deposition time and 15L/min acetylene flow rate.
iv
Abstrak tesis yang dikemukakan kepada Senat Universiti Putra Malaysia sebagai
memenuhi keperluan untuk ijazah Master Sains
SINTESIS DAN PENCIRIAN BAHAN NANO KARBON DI ATAS KARBON
FIBER PENDEK MENGGONAKAN REAKTOR LAPISAN TERBENDALIR
PENGURAIAN WAP KIMIA DAN FABRIKASI NANO KOMPOSIT KARBON
Oleh
MAHTA SADEGH VISHKAEI
Oktober 2009
Pengerusi : Dr. Mohamad Amran B. Mohd Salleh
Fakulti : Kejuruteraan
Dalam kajian ini, satu kajian awal telah dilakukan untuk menerangkan pengaruh
parameter dan mengkaji kesan (i) suhu sintesis, (ii) jenis pemangkin dan (iii) halaju
gas sumber karbon ke atas kualiti CNT yang dihasilkan melalui proses FBCVD.
Sintesis nano tiub karbon (CNTs) telah dijalankan melalui penguraian gas asetilena
bermangkin ke atas pemangkin Fe/CF (menggunakan kaedah penyediaan impregnasi)
di dalam reaktor lapisan bergerak. Keperluan pertumbuhan secara umumnya adalah
seperti berikut: halaju gas 40 lit/min, suhu sintesis 450-650 °C, tekanan atmosfera dan
tiga komposisi gas: 50%, 25% and 25% C2H2/H2/N2. Substrat pemangkin yang
digunakan ialah gentian karbon pelbagai saiz (1mm dan 2mm) dan pelbagai
komposisi besi (0.23%, 1.8% dan 4.92%) digunakan untuk dimendapkan di atas
permukaan CF. Struktur pemangkin dan produk yang terhasil kemudiannya dicirikan
dengan menggunakan pola X-Ray Diffraction (XRD), Scanning Electron Microscope
(SEM) dan Thermal Gravimetric Analysis (TGA). Satu pertalian ketara dapat dilihat
di antara kandungan besi metalik di dalam pemangkin, saiz substrat dan pencirian
akhir produk karbon yang terhasil. Kemudian komposit nano disediakan dengan nano
tiub berkualiti terbaik dan juga polipropilena dengan komposisi masing-masing
v
adalah 2% dan 98%. Campuran itu kemudiaannya dimasukkan ke dalam pengadun
(Halaju rotor dan suhu masing-masing ditetapkan kepada 120 rpm dan 180 oC dan
diadun selama 10 minit). Akhirnya, analisa komposit telah dijalankan menggunakan
Dynamic Mechanical Analysis (DMA) untuk menentukan sifat mekanikalnya. Kajian
ini menunjukkan kondisi optimum untuk kadar pertumbuhan CNT ialah 600 °C untuk
1.8% Fe ke atas gentian karbon dengan panjang 2mm untuk 30 minit masa
pengendapan dan 15 L/min halaju gas asetilena.
vi
ACKNOWLEDGEMENTS
In the name of God, Most gracious, Most merciful All gratification are referred to God
I would like to take this opportunity to express my highest gratitude and thanks to my
supervisors committee, Dr. Mohamad Amran Mohd Salleh, Assoc. Prof. Dr. Robiah
Yunus and Dr. Dayang Radiah Awang Biak for their time, support, advises,
encouragement and constant guidance throughout the completion of my study. And
most of all, for given me chance to improve myself to be a better person in real life.
Special appreciation to Assoc. Prof. Dr. Robiah Yunus for serving as my thesis co-
director and committee member. She provided valuable feedback and assistance as
well as financial support during early stages of my program of study. I would also
like to thank:
My mother, Mrs. M. Davoodi and my father, Mr. H. S. Vishkaei:
“For all those times you stood by me
For all the truth that you made me see
For all the wrong that you made right
My husband Mr. A. Ahmadi
For all the joy you brought to my life
For every dream you made come true
For all the love I found in you
I'll be forever thankful you’re the ones who held me up Never let me fall you’re
the one who saw me through
Through it all”
Finally, special thanks to my kind and respectful aunt, Mrs.H.Davoodi, my best
friend in Malaysia and her respectful family, for their support and encouragement,
and also my uncle Mr.D.Davoodi for lightening me when I found the going tough .
vii
I certify that an Examination Committee met on October 2009 to conduct the final
examination of Mahta Sadegh Vishkaei on her master of science thesis master thesis
entitled " Synthesis of carbon nanoparticles on short carbon fiber by fluidized bed
chemical vapour deposition (FBCVD) and fabrication carbon nanocomposite" in
accordance with Universiti Pertanian Malaysia (Higher Degree) Act 1980 and
universiti Pertanian Malaysia (High Degree) regulation 1981. The Committee
recommends that the student be awarded the relevant degree.
Member of the Examination Committee are as follows:
(Chairman)
Prof. Dr. Abdul Halim Shaari
Faculty of Science
Universiti Putra Malaysia
(Internal Examiner)
Dr. Suraya Abdul Rashid
Faculty of Engineering
Universiti Putra Malaysia
(Internal Examiner)
Prof. Ir. Dr. Mohd. Shobri Takriff
Faculty of Engineering
Universiti Putra Malaysia
(External Examiner)
Prof. Madaya Ir. Dr. Thomas Choong Shean Yaw
Faculty of Engineering
Universiti Putra Malaysia
Bujang Kim Huat, PhD
Professor/ Deputy Dean
School of Graduate studies
Universiti Putra Malaysia
Date:
viii
This thesis submitted to the Senate of Universiti Putra Malaysia has been accepted as
fulfilment of the requirement for the degree of Master of Science.
Members of the Supervisory Committee were as follows:
Mohamad Amran B. Mohamad Salleh, Phd. Lecturer
Faculty of Engineering
Universiti Putra Malaysia
(Chairman)
Assoc. Prof. Dr. Robiah Yunus, Phd.
Associate Professor
Faculty of Engineering
Universiti Putra Malaysia
(Member)
Dr. Dayang Radiah Awang Biak, Phd.
Lecturer
Faculty of Engineering
Universiti Putra Malaysia
(Member)
HASANAH MOHD GHAZALI, PhD
Professor and Dean
School of Graduate studies
Universiti Putra Malaysia
Date: 11 February 2010
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DEDICATION
I hereby declare that the thesis is based on my original work expect for quotations and
citations which have been duly acknowledged. I also declare that it has not been
previously or concurrently submitted for any other degree at UPM or other
institutions.
MAHTA SADEGH VISHKAEI Date: 11 February 2010
x
TABLE OF CONTENTS
Page
ABSTRACT ii
ABSTRACT iv
ACKNOWLEDGEMENTS vi
APPROVALS vii
DEDICATION ix
LIST OF TABLE xii
LIST OF FIGURES xiv
LIST OF ABBREVIATIONS xvii
CHAPTER
1 INTRODUCTION
1.1 Background of study 1
1.2 Objective of the study 8
1.3 Scope of study 8
1.4 Structure of thesis 9
2 LITERATURE REVIEW
2.1 Carbon Nanoparticles 10
2.2 Mechanism of carbon nanoparticles growth 16
2.3 Motivation for Large-Scale Synthesis
of Carbon Nanoparticles 20
2.4 Carbon Nanoparticles Synthesis Techniques 21
2.4.1 Arc Method 23
2.4.2 Laser Methods 25
2.4.3 Chemical Vapour Deposition 26
2.5 Fluidized-Bed Technology 29
2.5.1 Advantages of Fluidized Beds 31
2.6 Studies of carbon nanoparticles synthesis using Fluidized-Bed
C Chemical Vapour Deposition (FBCVD) 34
2.7 Effect of operation parameters on CNPs growth 34
2.7.1 Effect of temperature on CNT growth 34
2.7.2 Influence of Carbon Source 36
2.7.3 Influence of catalyst 37
2.7.4 Influence of Additives 47
2.8 Whiskerization 51
2.9 Polypropylene 52
2.10 Nanocomposites 53
xi
3 MATERIALS AND METTHOD
3.1 Introduction 55
3.2 Catalyst preparation 55
3.2.1 Cutting the carbon fiber 56
3.2.2 Making the deposit of Fe over CF 56
3.2.3 Use EDX and XRD to find the concentration the Fe 57
over the CF
3.3 Synthesis process of carbon nanoparticles 58
over the carbon fiber 59
3.3.1 Minimum velocity 58
3.3.2 Preparation the reactor 60
3.3.3 Operating condition 61
3.4 Characterization
3.4.1 Scanning Microscopy Electron 64
3.4.2 Thermo Gravimetric Analysis (TGA) 65
3. 3.4.3 X-ray Diffraction (XRD) 66
3.5 Composite preparation
3.5.1 Preparation of nano composite 68
3.5.5 Specimen for testing 70
4 RESULTS AND DISCUSSION
4.1 Introduction 73
4.2 Catalyst characterization 73
4.2.1 XRD results 74
4.2.2 EDX results 75
4.2.3 SEM results 78
4.3 Investigate the operating conditions of CNP growth 80
4.3.1 Effect of Iron concentration on CNP grown 80
4.3.2 Effect of CF size on CNP grown 85
4.3.3 Effect of Acetylene flow rate on CNP grown 87
4.3.4 Effect of temperature on CNP grown 92
4.4 Composite characterization 97
4.4.1 Effect of whiskerized carbon fiber on tensile
properties of composite 101
4.4.2 Effect of coated carbon fiber on thermal 104
property of WCF/PP Composite
5 CONCLUSION AND RECOMMENDATIONS
5.1 Conclusions 114
5.1.1 Catalyst characterization (Fe over the CF) 115
5.1.2 Effect of CF size on CNP grown 115
5.1.3 Effect of Acetylene flow rate on CNP grown 115
5.1.4 Effect of temperature on CNP grown 115
5.1.5 Nanocomposite characterization 115
5.2 Recommendations 116
xiii
LIST OF TABLES
Table Page
2.1 Specific Tensile strengths of various materials 15
2.2 Comparison of the Established Techniques for CNT Synthesis 22
3.1 Quantity of Iron Nitrate and carbon fiber 57
3.2 Different operating condition 63
3.3 Different type of composite 68
4.1 Effect of reaction temperature on CNPs production 93
4.2 Tensile results for PP, CF/PP, WCF/PP 102
xiv
LIST OF FIGURES
Figure Page
1.1 Electron configuration of carbon atom 1
1.2 Caps to SWNT formed by cutting a fullerene C60 2
molecule along the equatorial plane, (a) shows the
armchair cap normal to a fivefold axis while (b)
shows the zigzag normal to a threefold axis
2.1 Eight allotropes of carbon: a) Diamond, b) Gaphite, 10
c) Lonsdaleite, d) C60 (Buckminsterfullerene or
buckyball), e) C540, f) C70, g) Amorphous carbon,
and h) single-walled carbon nanotube or buckytube
2.2 (a) Definition of the chiral vector describing the 12
unit cell of a SWNT (b) images of armchair (n, n),
zigzag (n, 0) and chiral nanotubes Details of structural
parameters
2.3 single wall carbon nanotube 14
2.4 Schematic of the proposed interacting 18
particle model for nanotube initiation and
growth. Shading is representative of carbon
concentration. Bold arrows indicate the
direction of diffusive flux. Clear arrows
indicate the direction of particle motion.
2.5 Impact of increasing gas-phase availability 19
and associated increase in surface deposition
flux and possible
2.6 Arc-discharge scheme. Two graphite electrodes 24
are used to produce a dc electric arc-discharge
in inert gas atmosphere.
2.7 Sketch of a typical fluidized-bed reactor 31
setup. A cylindrical reactor is affixed within
a high-temperature furnace with appropriate
temperature, pressure, and gas flow controls,
connected to a data logging system. Environmental
xv
mitigation systems are incorporated to remove
entrained solid particles in the off-gas before
venting to atmosphere.
2.8 Circulating fluidized bed reactor 33
2.9 Synthesis of CNTs from substrate- 41
bound catalyst particles: (a) growth mechanism
by incorporation of carbon at catalyst particle
which remains at base of CNT, (b) critical steps
of catalyst preparation, annealing, and CNT
nucleation and growth
3.1 Universal Cutting Mill Machine Pulverisette 19 56
3.2 Measure the differential pressure based on flow rate 59
3.3 Fluidized bed reactor set up 61
3.4 Thermo Haake PolyDrivewith Rheomix 69
R600/610 blending machine
3.5 Toyoseiki Mini Test Hydraulic Hot and Cold Press 70
3.6 Q800 TA Instrument DMA Q800 V7.1 Build 116. 71
Dynamic mechanical analyzing machine
4.1 Sample XRD result for decomposition of iron 74
on carbon fiber surface
4.2 Typical EDX spectrum of Fe nanoparticles 76
(a) and composition as measured by EDX in
SEM (b), at 0.23% Fe over 2mm CF.
4.3 EDX measured 1.8% Fe over 1mm CF 77
4.4 EDX measured 4.92% Fe over 2mm CF 77
4.5 SEM image of Fe catalyst decomposed 79
on 1mm carbon fiber with 1.8%Fe
4 .6 SEM image of Fe catalyst decomposed 79
on 1mm carbon fiber with 4.92%Fe
xvi
4.7 SEM image for CNT with 0.23% Fe-CF 81
4.8 SEM image for CNT with 1.8% Fe-CF 82
4.9 SEM image for CNT with 4.92% Fe-CF 82
4.10 TGA result for 0.23%, 1.8% and 4.92% Fe-CF 84
4.11 CNT produced at different iron concentration 85
per 2 g of catalyst
4.12 TGA result for different size of CF (1mm and 2mm) 86
4.13 SEM image for 10L/min acetylene flow rate 88
4.14 SEM image for 20L/min acetylene flow rate 89
4.15 TGA result for different acetylene flow rate 90
4.16 CNT produced for different acetylene flow rate 92
4.17 SEM images of CNT gown on Fe/CF at a) 94
600oC and b) 450
oC
4.18 SEM images CNT gown at a) 550oC and b) 500
oC 95
4.19 CNT produced at different temperature 96
4.20 XRD result for CNT gown at 650oC 97
4. 21 XRD results of CNT growth with various 98
growing temperatures
4.22 TGA results of CNTs growth processed at 100
various reaction temperatures
4.23 SEM images of CF after Fe nanoparticle 101
deposition on it (a) and CF surface after
growing carbon naotube(b)
4.24 TGA curves of PP, CF/PP and CNT/PP composite 105
4.25 DTA-TGA result for 2% coated CF with 106
nanoparticles /PP composite
4.26 Storage modulus (E’) of unfilled PP, CF/PP 108
and CNT/PP composite
xvii
4.27 Loss modulus (E’’) of unfilled PP, CF/PP 110
and CNT/PP composite
4.28 Tangent δ of unfilled PP, CF/PP and CNT/PP composite 112
xviii
LIST OF ABBREVIATIONS
ARNT Array of Carbon Nano Tube
ASTM American Society for Testing Materials
β Maximum of the XRD peak
CAT Catalyst
CCVD Catalyst Chemical Vapour Deposition
CVD Chemical Vapour Deposition
CNT Carbon Nano Tube
CNP Carbon Nano Particle
CNM Carbon Nano Material
DC Direct Current
DMA Dynamic Mechanical Analysis
DNA Deoxyribo Nucleic Acid
DSC Differential scanning Calorimetry
TDA Thermal Differential Analysis
E' Storage Modulus (MPa)
E" Loss Modulus (MPa)
EDX Energy Dispersive X-ray
EDS Energy Dispersive Spectroscopy
EDXRF Energy Dispersive X-Ray Fluorescence
FBCVD Fluidized Bed Chemical Vapour Deposition
HIPCO High Pressure Carbon Monoxide
ID Internal Diameter
xix
LC Mean Crystalline Size (along the c-axis)
λ Wavelength of X-rays
M Weight
MWCNT Multi Wall Carbon Nano Tube
PECVD Plasma Enhanced Chemical Vapour Deposition
PP Poly Propylene
SEM Scanning Electron Microscopy
SWCNT Single Wall Carbon Nano Tube
TAN δ Tangent Delta
SCF Short Carbon Fiber
TGA Thermal Gravimetric Analysis
Tonset Degradation Temperature
Tm Melting temperature
Tg Glass Transition temperature
θ Angle corresponding to the peak of XRD
Umf Minimum Velocity
U Velocity
VPSEM Scanning Electron Microscope Environmental
XRF X-ray fluorescence
XRD X-ray diffraction
CHAPTER 1
INTRODUCTION
1.1 Background of study
Carbon, with an electronic ground state arrangement of 1s2 2s
2 2p
2, has the ability to
form four valence orbitals: 2s, 2px, 2py, and 2pz (Figure 1.1). The mixing of the 2s
and 2p atomic orbitals is known as hybridization. Three possible hybridization states
(sp1, sp
2, and sp
3) have resulted in many important carbon structures, including
carbon nano particles (CNPs). Before the discovery of fullerenes, two solid elemental
carbons were believed to exist in only two crystalline phases: graphite and diamond,
exhibiting sp2 and sp
3 hybridized bonding, correspondingly. The structure of large
carbon clusters with >40 carbon atoms remained unsolved until Kroto et al.
synthesized fullerene C60 in 1985 and postulated its structure as that of a shortened
icosahedrons (Chee et al., 2007).
Figure 1.1. Electron configuration of carbon atom (Source: http://intro.chem.okstate.edu/1215/Lecture/Chapter11/Fri112098.html)
2
There are different types of CNTs, due to the feet that the graphitic sheets can be
rolled in many ways. The three types of CNTs are Zigzag, Armchair, and Chiral. It is
possible to recognize zigzag, armchair, and chiral CNTs just by following the pattern
across the diameter of the tubes, and analyzing their cross-sectional structure
(Michael et al., 2002). Figure 1.2 explains two types of CNTs.
Figure 1.2: Caps to SWNT formed by cutting a fullerene C60 molecule along the
equatorial plane, (a) shows the armchair cap normal to a fivefold axis while (b)
shows the zigzag cap normal to a threefold axis (Source: Dresselhaus, 1992)
Carbon nanotubes (CNTs) have been investigated for a multitude of applications
including energy storage, field emission devices, and composite material
strengthening, because of their exclusive mechanical, optical, and electrical properties.
Both multiwalled (MWCNTs) and single-walled (SWCNTs) carbon nanotubes can be
used, depending on the value-added functionality required in the product. On the
other hand, the use of CNTs in both research and end-user applications is currently
limited by production throughput. Of the three main techniques used for CNT
synthesis, that is, laser ablation, arc discharge, and chemical vapour deposition
(CVD), the latter is recognized as having the most potential for large-scale,
economically viable CNT production (Venegoni et al., 2002).
3
Carbon nanotubes (CNTs) are attractive materials with a wide range of potential
applications. Various CNT based electronic devices, such as transistors (Weitz et al.,
2007; Tans et al., 1998) logical circuits (Bathold et al., 2001) nano electromechanical
devices (Ke and Espinosa , 2006; Rueckes et al., 2000) sensors (Brian et al., 2007;
Park et al., 2006) have been established. In 1995 field emission from CNTs was
reported (Rinzler et al., 1995, Deheer et al., 1995) and nanotubes becomes promising
candidates as a field electron emitters. The high aspect ratio (length to diameter) of
the CNTs results in a high field improvement factor, useful to field emission. These
applications demand an unusual combination of material properties, such as structural
rigidity, electric conductivity and small density, possessed only by CNTs. Electronic
devices should also resist high temperatures caused by Joule heating and high tensile
stresses to keep away from device failure (Wong et al., 2003, Pan et al., 2001).
One of the most promising uses of CNTs is in the development of nano composites,
where the CNTs are used as novel fillers and binders to improve their mechanical,
electrical and thermal properties. CNTs have great potential applications due to their
very large aspect ratio (1000–10,000), low density, high rigidity (Young's modulus of
the order of 1 TPa), and high tensile strength (up to 60 GPa). In addition, the
excellent electrical conductivity (106 S/m at 300 K for single-walled CNT (SWCNT)
and >105 S/m for multi-walled CNT (MWCNT)) and thermal conductivity
(6600 W/mK for an individual SWCNT and >3000 W/mK for an individual
MWCNT) make them suitable candidates in preparing nanocomposites with new
functional properties (Kumaria et al., 2008).
4
It has been established in recent years that polymer based composites reinforced with
a small percentage of strong fillers can significantly improve the mechanical, thermal
and barrier properties of pure polymer matrix (Mahfuz et al., 2004). When these
fillers are rod-shaped, the surface area per particle will lead to high mechanical
strength and stiffness in axial direction and because of this they are considered the
most interesting fillers for advanced applications composites. Carbon fiber reinforced
composites have all the ideal properties, leading to their rapid development and
successful use for many applications over the last decade (Chung, 1994). Although
the carbon fiber polypropylene composite yields catastrophically, it bears a higher
load than the glass fiber polypropylene composite, resulting in higher flexural
strength. The effect of carbon fiber content and fiber length on mechanical and
thermal properties of SCF/PP has already been studied (Fateme, 2006).
The good composite performance often depends on the degree of adhesion between
the fiber and the resin binder. Adhesion is usually controlled by chemical bonding
due to functional groups and by mechanical interlocking due to surface morphology
and this leads researchers to develop a number of surface treatments that could
improve the fiber matrix polymer interfacial bonding. Whiskerization treatment on
carbon fibers was an effective way to increase the shear strength of carbon-epoxy
composite materials by 400%. Whiskerization involves carbon nanoparticles growth
on the surface of carbon fibers. The total surface area would increase, and enhance
the mechanical interlocking between fibers and matrixes (Rebouillat, 1984).
5
Since nanoparticles can be grown by different methods with different parameters, the
selection of a suitable type of CNP synthesis for a selective application is
challenging. The CNTs can be prepared by various methods such as arc discharge,
laser ablation, chemical vapour deposition (CVD) and others with CVD the most
widely used method of production. Among the different techniques that have been
applied for the processing of carbon nanotubes (CNTs) (Journet and Bernier, 1998)
catalytic chemical vapour deposition (CCVD) appears promising in opinion due to its
relatively low cost and potential high yield production. Definitely, this method,
originally used to prepare carbon filaments (Rodriguez, 1993) or vapour-grown
carbon fibers (De and Geus, 2000; Endo, 1998) also could be effective for the growth
of nanotubes. In fact, precursors of filaments or vapour-grown carbon fibers were
evidenced as having nanotubular structure (Toan et al., 1999; Serp and Figueiredo,
1996; Endo et al., 1995). The CCVD technique has been applied both in the absence
and in the presence of a substrate. The earlier is a gas phase homogeneous process,
the latter is a heterogeneous process. Although more scarce studies on homogeneous
processes have demonstrated, that it was possible to produce selectively multiwalled
carbon nanotubes (MWNTs) (Marangoni et al., 2001), single-walled carbon
nanotubes (SWNTs) (Satishkumar et al., 1998, Cheng et al., 1998), or arrays of
carbon nanotubes (ARNTs) (Rao et al., 1998).
Heterogeneous processes have been explored more intensively and MWNTs
(Piedigosso et al., 2000; Ivanov et al., 1995), SWNTs (Colomer et al., 2000; Hafner
et al., 1998) have been produced on supported or bulk catalysts. Currently, the use of
bulk metal catalyst leads mainly to the production of carbon filaments, also called